1. Technical Field
This invention relates to a liquid treating equipment which injects a liquid into a vessel through an injection tube by a liquid supplying means and discharges, in order to maintain the liquid level in the vessel to a given value, the excess amount of the liquid through an injection tube with a suction inlet provided at the same level of the vessel as the liquid level by a liquid discharging means.
2. Background Art
Small capacity vessels are employed in a variety of fields such as chemical analysis, pharmaceutical analysis and medical care. That is, in such a field as biochemical, molecular biology and medical cure, since it is often difficult to generate and extract-purify a substance to be used in a chemical reaction, the substance must be often obtained through its chemical reaction of a small amount of liquid in a small capacity reaction vessel. Normally, as liquid chromatography, the small capacity vessel has a built-in or continuously joined injection port and discharge port thereto provided above a level position of the vessel, and a liquid is injected into the vessel from the injection port and discharged from the discharge portion.
The above conventional small capacity vessel is perfectly sealed. However, such a sealed structure restricts the function of the small capacity vessel. For example, it is difficult to transform and move a transducer to transmit the condition of the inside of the vessel to outside. If possible, a very complicated mechanism is required.
Recently, for operating such a transducer freely, a top-opened vessel is employed. Attention must be paid to the evaporation of the liquid if the top-opened vessel is employed for treating the liquid. If the top-opened vessel has a top opening with an area of 10 mm2 and below and a depth of 3 mm in order to fill a liquid of 10–15 μl in, the degree of the evaporation is remarkably developed, resulting in the change of the volume and concentration of the liquid and thus, the remarkable change in its hydrogen-ion concentration (pH). These parameters influences the analytic results and experimental results of the liquid.
To iron out the above matter, a liquid treating equipment to supply an additional liquid constantly during the chemical reaction or the experiment of the liquid is employed. In the liquid treating equipment, the additional liquid is injected constantly into the top-opened vessel through an injection tube in order to replenish the evaporated amount of the liquid. In using such a liquid treating equipment, since the fluctuation of the liquid level of the liquid to be filled in influences largely the experiment or the chemical reaction of the liquid, it is required to maintain the liquid level.
Generally, for maintaining the liquid level with injecting the additional liquid constantly, an excess amount of the liquid is overflown out of the vessel, but if the small capacity vessel with its small opening is employed, its liquid level is risen by its surface tension when the additional liquid is injected. Then, if the liquid level is risen beyond a given level, the surface tension is broken and thus, the excess amount of the liquid is overflown. In the case of using the small capacity vessel, such a process is repeated, so that the liquid level is largely fluctuated and the liquid level can not be maintained to a desired level. Therefore, for repressing the fluctuation of the liquid level, a discharge tube is provided at the desired liquid level position of the vessel, and the excess amount of the liquid beyond the desired liquid level is discharged out of the discharge tube.
In a liquid treating equipment having an injection tube and a discharge tube to inject an additional liquid constantly and discharge the excess amount of the liquid as its liquid level is overflown in order to maintain the liquid level constant, if the equipment has a small capacity vessel with an opening of several square millimeter, it can not have its desired liquid level due to large fluctuation.
FIG. 1 shows a fluctuation state of a liquid level in a conventional liquid treating equipment. A vessel 1 is composed of a base block with a concave portion therein. Then, an injection tube 3 is provided so that its injecting inlet can be positioned at a lower level position than a desired liquid level, and a discharge tube 4 is provided so that its discharging inlet can be positioned at the same level position as that of the desired liquid level.
An upper left view in FIG. 1 shows the state in which the risen liquid level through the injection of the additional liquid into the vessel 1 from the injection tube 3 is just contacted to the discharging inlet of the discharge tube. In the state, the liquid level is almost equal to the desired liquid level L despite of the liquid level wave. If an additional liquid is injected into the vessel in the state as shown in the upper left view in FIG. 1, the excess amount of the liquid in the vessel is discharged through the discharge tube 4. In this case, as shown in a central view in FIG. 1, if the liquid level comes down below the desired level, the liquid is discharged to some degree, so that the liquid level waves largely. Thereafter, as shown in upper right view in FIG. 1, the liquid level is discontinued to the discharging inlet of the discharge tube 4 because it is situated at a lower position than the desired liquid level L. Subsequently, if an additional liquid is injected through the injection tube 3, the liquid level is risen and has the initial state as shown in the upper left view. Since the above process is repeated, the liquid level is fluctuated largely.
Although the conventional liquid treating equipment has the injection tube 3 and the discharge tube 4, the liquid level fluctuates largely and thus, can not have the desired liquid level. It is considered that the liquid level fluctuation results from two phenomena as follow.
First of all, it is considered that a pump, as the additional liquid is injected by a pump, beats the liquid level through the beaten additional liquid. An air pump as a commercially available pump beats the liquid level inevitably, and fluctuates the liquid level largely. Moreover, a positive displacement pump in which its plunger moves in its cylinder back and forth may be employed as a smaller beat liquid pump, but has difficulty in repressing the liquid level fluctuation if the vessel 1 has a small capacity of μl order.
Second, in the above state, the liquid in the vessel is contacted to an air surrounding the vessel. At the interface between the liquid and air with the respective different phases, the liquid tends to have its minimum surface area due to their different agglutination, and the liquid level is risen in cone around the discharge tube by capillary phenomenon. That is, the liquid level has a depressed shape as a whole and a conical rising shape around the discharge tube, so that the liquid level is fluctuated largely.
Due to the above two phenomena, the liquid level is partially risen around the discharge tube and discharged as before even though the bottom surface of the depressed liquid level comes down below the discharging inlet of the discharge tube. If the absorption force for the discharge tube due to the surface tensile of the liquid becomes smaller than the weight of a part of the liquid around the discharge tube, the part of liquid level is separated from the discharge inlet of the discharge tube, and thus, falls down. The liquid level is risen through the shutdown of the liquid discharge and the injection of an additional liquid from the injection tube to contact the discharging inlet of the discharge tube. As the liquid has a smaller surface area, it has a largely curved liquid level, so that in the case of employing a small capacity vessel, the liquid level is remarkably fluctuated.
As mentioned above, in the conventional liquid treating equipment having the small capacity vessel, the beat of the additional injected liquid from the pump and the surface tensile and capillary phenomenon of the liquid fluctuate the liquid level largely not to maintain the liquid level to the desired level. The largely fluctuated liquid level changes the dipped length of a probe of a transducer in the liquid, resulting in the analytic error and measurement error of the liquid.
In view of the above matter, it is an object of the present invention to provide a liquid treating equipment, through the mitigation for the above conventional matter, which can maintain a liquid level of a liquid filled in a vessel to a desired level even though the injected liquid is beaten, and thus, make as small as possible errors in the analytic results or measurement results of the liquid due to the fluctuation of the liquid level.